1. Field of the Invention
The present invention relates to a reinforcing support structure for a three-wheeled motor vehicle, and to a three-wheeled vehicle incorporating the described reinforcing support structure. More particularly, the present invention relates to a reinforcing support structures and to a three-wheeled motor vehicle in which a main frame cage is pivotally rockable about a rocking axis, with respect to a rear wheel support structure.
2. Description of the Background Art
One example of a known power transmission for a vehicle has rear wheels attached at the tips of right and left axles that extend concentrically from a differential gear to the right and left sides of the vehicle body, respectively. Examples of this type of design can be found in Japanese published patent documents JP-UM-B-63-21445 (page 2, FIG. 3) and in JP-UM-B-59-106723 (pages 4 to 5, FIG. 3).
FIG. 25 of the appended drawings is a reproduction of FIG. 3 from Japanese published patent document JP-UM-B-63-21445, and is included herein for comparative discussion purposes. Here, reference numerals are changed from those used in the original.
FIG. 25 is a top plan view showing a power transmission mechanism of a conventional three-wheeled motor vehicle. Shown therein is a vehicle 300 in which an output of an engine 301 is transmitted to a differential gear 304 via chains 302 and 303. In the prior art vehicle 300 illustrated in FIG. 25, rear wheels 307 and 307 are respectively rotatably attached to the outer tip ends of rear wheel axles 305 and 306, which extend from the differential gear 304, in opposite directions, to the sides of the vehicle. With such a structure, the rear wheels 307 and 307 are driven.
In the vehicle shown in FIG. 25 above, the rear wheel axes 305 and 306 are extended, to right and left, from both sides of the differential gear 304, to be coupled with the rear wheels 307 and 307. With such a placement, if the right and left rear wheels 307 and 307 are to be independently suspended, the right and left rear wheels 307 and 307 are each attached to the vehicle body side in such a manner as to move in the vertical direction via each corresponding suspension arm. The rear wheel axes 305 and 306 are used in a drive shaft including a constant velocity joint, for example.
The drive shaft can transmit the driving forces to the rear wheels 307 and 307 even if the rear wheels 307 and 307 move in the vertical direction. For such transmission, however, the pivot angle of the constant velocity joint being a part of the drive shaft has to be a predetermined angle or smaller. Accordingly, if the total length of the drive shaft is short, it will cause difficulty in reducing such a pivot angle.
In order to make the pivot angle relative to the drive shaft equal to or smaller than the predetermined angle, there is a need to increase the total length of the drive shaft. As a result, the distance between the centers of the right and left rear wheels, i.e., the tread (or wheel base), which denotes a horizontal distance between the centers of right and left tire tracks contacting the road surface) is increased, thereby rendering the vehicle wider. Thus, it is hardly applicable to small-sized vehicles, resultantly impairing the vehicle mobility.
FIG. 26 of the appended drawings is a reproduction of FIG. 3 from Japanese published patent document JP-UM-B-59-106723. Here, reference numerals are changed from those used in the original.
FIG. 26 is a cross-sectional view of a transmission of a conventional three-wheeled motor vehicle. Shown therein is a portion of a vehicle powertrain, in which an engine 311 is coupled with an automatic belt-driven transmission 312, and a differential gear 314 accommodated in a gear box 313 is coupled with the belt-driven automatic transmission 312 via gears and chains, and rear wheel axles 316 and 316 are attached, respectively, to the right and left sides of the differential gear 314. Rear wheels 317 and 317 are attached, respectively, to these rear wheel axles 316 and 316.
Although the known devices have some utility for their intended purposes, there is still a need to provide an improved three-wheeled motor vehicle and reinforcing support structure therefor. More particularly, there is a need for an improved three-wheeled motor vehicle and related support structure, in which a main frame cage can pivotally rock about a rocking axis with respect to a rear wheel support structure.